The present invention relates to the field of medical catheters.
In man and many other species urine is stored in a bladder before it is released. Urinary bladders are generally elastic to accommodate varying volumes, and tend to shrink when the bladder in not made to expand over relatively long periods of time. A significant problem exists in individuals that are catheterized for more than a few days at a time, because the catheters are often left in an open (draining) position to avoid excessive buildup of pressure. Unfortunately, leaving catheters in an open position for long periods of time greatly increases the risk of infection.
Many catheter designs have been developed to overcome these problems. A good review is set forth in U.S. Pat. No. 6,050,934 to Mikhail et al. (April 2000), which is incorporated herein by reference in its entirety. The more prevalent types of valves for use with catheters in discharging urine are those that are manually-operated. When the bladder fills with urine to the level where an individual needs to urinate, the individual opens the valve and it consequently releases the urine. The valve then shuts after release of the urine. Examples of manually-operated valves are discussed in U.S. Pat. No. 4,946,449 (August 1990) to Davis Jr.; U.S. Pat. No. 4,932,938 to Goldberg et al. (June 1990); and U.S. Pat. No. 4,846,784 to Haber (July 1989), each of which is incorporated herein by reference in its entirety.
Drawbacks generally are associated with the use of manually-operated valves in catheters. If an inadvertent, slight force is exerted to certain areas, the valve can open, thereby allowing urine to flow. For instance, force can be placed on an external valve if it is pressed between an individual""s legs when the legs are crossed. If so, urine can be released and the individual can be embarrassed by the unintended failure of the catheter valve to retain the urine. Furthermore, many of the valves are difficult to operate and require much more force to operate than can be applied by some individuals. U.S. Pat. No. 6,050,934 to Mikhail et al. (April 2000) provides a manually-operated valve that reduces the amount of force required for the individual to operate, at the time that protection is needed, to help minimize inadvertent or unintended operation of the valve resulting in the unintended release of urine. However, an individual who has no feeling in the bladder region or who has no hand-control cannot operate the valve of the Mikhail ""934 patent to control urine flow. In addition, manually-operated valves close unreliably under normal pressures as is generally desired, and inadequately drain small aliquots of urine from within the valve. The small aliquots of urine not drained from the valve can transmit contaminants from the outside environment and cause infection in the bladder. Yet another problem with manually operated valves is that they are not especially useful for individuals that may be unconscious, or do not have use of their hands.
Automatic valves eliminate the need for an individual to operate a valve to control urine flow. An individual who has no feeling in the bladder region or who has no hand-control can rely on an automatic valve to release urine when the bladder needs to be emptied. An example of an automatic valve can be found in U.S. Pat. No. 5,114,412 to Flinchbaugh (May 1992), the disclosure of which is incorporated herein by reference.
A drawback of many known automatic valves, however, including the valves of Flinchbaugh, is that some of the valve parts are disposed within the lumen of the catheter, and are therefore disposed in the urinary flowpath. Such valves are difficult to autoclave and therefore are problematic upon reuse. Contact with fluid may also deteriorate the valve over time. Furthermore, a valve that contacts urine in a urinary catheter can transmit contaminants from the outside environment and cause infection in the bladder.
Thus, there is a continuing need for an automatic valve that controls fluid flow in a manner that would be consistent with physiological requirements for urinary bladder expansion and contraction.
The present invention relates to devices and methods in which a valve has a flow restrictor positioned outside of a lumen of a tube, which transitions between an open configuration and a closed configuration. The valve further contains a closing mechanism that automatically positions the flow restrictor to the closed configuration when a pressure in a fluid within the lumen is below a low threshold pressure, and an opening mechanism that automatically positions the first flow restrictor to the open configuration when the pressure in the fluid within the lumen is above a high threshold pressure that is higher than the low threshold pressure.
The flow restrictor is preferably positioned outside the tube, although it may be positioned inside the wall of the tube, or even within the lumen of the tube. There may also be a second, downstream flow restrictor. The two flow restrictors may be contained in the same or in different housings.
The opening and closing mechanisms advantageously comprise a magnet, but may additionally or alternatively comprise any other suitable mechanism, including a solenoid.
A particularly advantageous class of embodiments exists where the tube comprises a catheter, and especially a urinary catheter. In such instances the valve stays shut long enough to provide sufficient pressure to expand the bladder, then stays open long enough to substantially drain the bladder. The process may be entirely automatic, and not dependent upon any external power source.
Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawing in which like numerals represent like components.